• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.489-497
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• 2002

Nonlinear behavior and large deformation cannot be analyzed using techniques based on linear theory. Nonetheless, they are emerging as gradually huge and complex structures. In addition, the optimum design of structure is necessary in the development of high-performance computation and numerical methods. as well as stricter design-criterion. Therefore, the structural problems in engineering that are limited to the linear region must be extended to the nonlinear region. Likewise, structural behavior must be accurately analyzed. In turn, this requires considering the expected problems beforehand. Only then can an efficient, economical, and optimized structure be designed. This paper presents the solution of the geometrical nonlinear problem of anisotropic cylindrical shell. The characteristics of the geometrical nonlinear behavior of anisotropic circular cylindrical shells may vary according to several causes. e.g., change of fibers, curvature in the circumferential direction, subtended angle, aspect, etc. Parametric studies were conducted to determine the effect of factors on the large deflection behavior of laminated shells, with interesting observations.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.3-10
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• 1990

Hull form can be described numerically by two approaches, one is to describe a hull form with a set of curves("curve approach"), and the other is to describe it with surfaces directly("surface approach"). This paper describes the numerical definition scheme of hull form using curve approach method which defines the hull form by a set of curves consisting of 2-dimensional transverse section curves and 3-dimensional longitudinal curves. A set of curves in the hull form definition scheme is described by the modified cubic spline which modified the general parametric cubic spline in order to ensure a very smooth curvature distribution within the curve segment even though a curve segment has large tangent angle at its end points. Illustrative examples are given showing the application of the method to represent the hull form of SWATH ship and oceanographic research vessel. Also, examples for hull form transformation are shown by using this method connected with transformation technique.

• Investigative Magnetic Resonance Imaging
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• v.20 no.2
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• pp.95-104
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• 2016

Purpose: To evaluate the knee joint after double-bundle anterior cruciate ligament (ACL) reconstruction with three-dimensional (3D) isotropic magnetic resonance (MR) image, and to directly compare the ACL graft findings on 3D MR with the clinical results. Materials and Methods: From January 2009 to December 2014, we retrospectively reviewed MRIs of 39 patients who had reconstructed ACL with double bundle technique. The subjects were examined using 3D isotropic proton-density sequence and routine two-dimensional (2D) sequence on 3.0T scanner. The MR images were qualitatively evaluated for the intraarticular curvature, graft tear, bony impingement, intraosseous tunnel cyst, and synovitis of anteromedial and posterolateral bundles (AMB, PLB). In addition anterior tibial translation, PCL angle, PCL ratio were quantitatively measured. KT arthrometric values were reviewed for anterior tibial translation as positive or negative. The second look arthroscopy results including tear and laxity were reviewed. Results: Significant correlations were found between an AMB tear on 3D-isotropic proton density MR images and arthroscopic proven AMB tear or laxity (P < 0.05). Also, a significant correlation was observed between increased PCL ratio on 3D isotropic MRI and the arthroscopic findings such as tear, laxities of grafts (P < 0.05). KT arthrometric results were found to be significantly correlated with AMB tears (P < 0.05) and tibial tunnel cysts (P < 0.05). Conclusion: An AMB tear on 3D-isotropic MRI was correlated with arthroscopic results qualitatively and quantitatively. 3D isotropic MRI findings can aid the evaluation of ACL grafts after double bundle reconstruction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.1
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• pp.1-7
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• 1976

1) The decrease in strength of netting twines at the knot may be regarded to be due mainly to the frictional force acting on the tip of the knot. The knot strength T may be given by $$T=\frac{T_0}{1+{\mu}\frac{s}{\rho}\varrho^{\mu\theta}$$ were $T_0$ is the tensile strength of unknotted netting twines, $\mu$ the coefficient of friction beween two netting twines forming a knot, s the contact length between the tip and the netting twine compressing it, $\rho$ the radius of curvature of the compressing, and $\theta$ the angle at which the compressing rubs with another one in the vicinity of the opposite tip. 2) Knots are arranged in order of strength as follows : the reef knot pulled lengthwise $\risingdotseq$ the trawler knot pulled breadtwise the reef knot pulled breadthwise.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.17-25
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• 2019

An intake of Aircraft becomes S-shaped geometry due to spatial limitation or procuring survivability. But curvature of the S-shaped geometry makes secondary flow or flow separation which is the cause of non-uniform pressure distribution. In this study, boundary layer suction is applied to RAE M 2129 S-Duct by attaching sub duct. Design variable is suction location and angle. A mass flow rate drawn out by suction at the sub duct outlet is constant over every model. A grid dependency test was conducted to verify validity of computation. The comparison among the CFD (Computation Fluid Dynamics), ARA experimental result, and ARA computation result of non-dimensional pressure distribution on the Port side and Starboard Side confirmed the validity of CFD. In this study, Distortion Coefficient was used for evaluating aerodynamic performance of S-Duct. The analysis, which was about flow separation, vortex, mass flow rate distribution, and pressure distribution were also investigated. Maximum 26.14% reduction in Distortion Coefficient was verified.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.712-719
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• 2019

This paper explores an implementation of finite element analysis and experiment in the design process of a tape spring hinge used for various CubeSat missions. Tape spring hinges consist of short-length hardened-steel strips with one-sided curvature, and thus the behavior is subject to large deformation with unpredicted non-linearity. Precise dimensions of a commercial tape spring are traced by the use of high-resolution digital camera, and thin-shell FEM analysis is conducted using ABAQUS program. Based on the rotation-moment analysis suggested in previous studies, parametric analysis is conducted by adjusting the contributing factors such as strip thickness and the subtended angle of the cross section. Finally the behaviors are investigated by both analytical and non-linear finite element methods, and the results are compared with the simple measurements. Further studies suggest a possible application in dynamic characteristics of hinges during CubeSat operations.

• Journal of Digital Convergence
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• v.19 no.8
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• pp.43-48
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• 2021

There are prior studies that describe in detail the classification and shape of 26 species of Korean flounder, but it is difficult to make them out and they are used interchangeably or misused. It is intended to present the taxonomic standards of Pleuronichthys cornutus and Pleuronichthys japonicus and use them as tourism education materials using aquatic resources. Morphological comparison was made through counting and measurement. The two fish species were generally flattened in an oval shape with a low body height and a wide body width, and the anal fin developed and sized similar to the dorsal fin, and the caudal fin was widely spread out. Among the hyoid bones, in three parts of the coccyx, the main part, the ischial part, and the cardinal process, there were differences in the degree of curvature, the open angle, and the shape of the ischial part and the lateral process, which corresponded to the representative classification characteristics. In addition, it will be expected that it will serve as a basis as a fishery and marine education material for marine tourism that classifies and categorizes the characteristics as a genus of flounder and categorizes the characteristics, and reduces misuse of scientific names and names in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.83-89
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• 2021

To improve the performance of self-driving cars, the introduction of V2X, a communication technology that connects vehicles, infrastructure, and vehicles, is essential. Even if traffic information of the other vehicle is known, the structure of the intersection and a distance calculation algorithm are required for accurate calculations at roundabouts. This paper proposes a design algorithm for a rotating intersection and implemented in Matlab that complies with the national design rules and enables accurate calculations. Assuming the roundabout and the entrance/exit path to be a circle, a method for measuring the distance between vehicles at an arbitrary point was proposed using the horizontal shift of the entrance circle to the main circle. The algorithm could be used in fully autonomous vehicles by designing a roundabout suitable for the terrain by arbitrarily varying the angle between branches and the radius of curvature of the entrance and exit roads, and transmitting a warning signal when a collision between two driving vehicles is expected.

• The Journal of Korean Physical Therapy
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• v.26 no.5
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• pp.358-364
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• 2014

Purpose: Flexed posture commonly increases with age in older women and is characterized by an excessive curvature in the thoracic spine (kyphosis), forward head posture, and decline in height. This study was conducted in order to determine the relationship between flexed posture, physical performance, and psychosocial factors in community dwelling elderly women in Korea. Methods: Fifty-two subjects with thoracic kyphosis of $40^{\circ}C$ or greater participated in this study. Flexed posture was measured using kyphosis angle (KA), forward head posture (FHP), and round shoulder (RS), and physical performance was evaluated using the short physical performance battery (SPPB), grip strength, and static and dynamic balance. Psychosocial factors were measured using depression and the quality of life (QOL). All data were analyzed using SPSS 18.0 software for windows. Results: KA showed significant correlation with SPPB score (r=-0.447) and dynamic balance (r=0.426) (p<0.05) depression (r=0.405) and QOL (r=-0.464) but not with grip strength and static balance in elderly individuals. FHP and RS showed significant correlation with SPPB score (r=0.002, r=-0341) and dynamic balance (r=-0.278, r=0.346) (p<0.05) but not with psychosocial factors. Conclusion: These findings suggest that flexed posture provides meaningful information about physical performance and psychosocial factors in elderly women. Our data suggest that the flexed posture may need to be addressed as part of the health management process for elderly women.

• Journal of KIISE
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• v.44 no.11
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• pp.1194-1208
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• 2017

A traditional average smoothing method is designed for smoothing out noise, which, however, unintentionally results in smooth corner points on the curvature accompanied with a shrinkage of curves. In this paper, we propose a novel curve smoothing method via polygonal approximation of the input curve. The proposed method determines the smoothing weight for each point of the input curve based on the angle and approximation error between the approximated polygon and the input curve. The weight constrains a displacement of the point after smoothing not to significantly exceed the average noise error of the region. In the experiment, we observed that the resulting smoothed curve is close to the original curve since the point moves toward the average position of the noise after smoothing. As an application to digital cartography, for the same amount of smoothing, the proposed method yields a less area reduction even on small curve segments than the existing smoothing methods.